羟基磷灰石与骨界面抗张强度测试及扫描电镜观察

本文测试了孔隙率为１４％，孔径小于２μｍ的纯羟基磷灰石（ＨＡ）与兔胫骨皮质骨之间界面的抗张强度，２周时为０．７２ＭＰａ；４、８、１６周之间强度无明显差异平均为１．５ＭＰａ。扫描电镜观察表明，２周时拉伸断裂位于ＨＡ－骨界面，４周以后多在ＨＡ晶体颗粒之间。ＨＡ与骨生物适应性好，矿化组织可以直接沉着于ＨＡ表面或ＨＡ内部，近界面处的ＨＡ发生了一定的生物降解反应，且骨矿化与ＨＡ的降解可能达到某种平衡。     

关于研究生课程"生物医学工程前沿"建设的意见

"生物医学工程前沿"是国家所规定的生物医学工程专业研究生的课程之一.它以极广的知识领域,最新的学术动态,最先进的医疗技术等为主要内容,展示该专业的研究范围、前沿动态、发展趋向及未来前景,是学生们全面了解本专业的最好窗口,也是获取专业知识的最丰富园地.     

冠状动脉支架抗压缩性能的有限元分析

冠状动脉支架作为经皮穿刺冠状动脉成形术中保持病变血管畅通的核心器件。其对病变动脉壁的支撑作用如何是支架植入术成功的先决条件之一。依据冠脉支架抗压缩性能的实际测试原型，建立起对应的有限元模型，并利用此方法系统地研究了专利支架设计，其扩张尺度的不同和筋的尺寸变化对支架抵抗两平面压缩性能的影响。结果显示，随支架扩张直径的增大，其抵抗两平面压缩的作用减小，增加支架筋的宽度或厚度能够提高支架的抗压缩性能，且这两个方向尺寸的增加对提高抗压缩性能的作用相当。模拟与实验结果一致，表明有限元模拟可以在一定程度上替代支架原型测试工作。     

Effects of massage on delayed-onset muscle soreness, swelling, and recovery of muscle function

Context: Delayed-onset muscle soreness (DOMS) describes muscle pain and tenderness that typically develop several hours postexercise and consist of predominantly eccentric muscle actions, especially if the exercise is unfamiliar. Although DOMS is likely a symptom of eccentric-exercise–induced muscle damage, it does not necessarily reflect muscle damage. Some prophylactic or therapeutic modalities may be effective only for alleviating DOMS, whereas others may enhance recovery of muscle function without affecting DOMS.Objective: To test the hypothesis that massage applied after eccentric exercise would effectively alleviate DOMS without affecting muscle function.Design: We used an arm-to-arm comparison model with 2 independent variables (control and massage) and 6 dependent variables (maximal isometric and isokinetic voluntary strength, range of motion, upper arm circumference, plasma creatine kinase activity, and muscle soreness). A 2-way repeated-measures analysis of variance and paired t tests were used to examine differences in changes of the dependent variable over time (before, immediately and 30 minutes after exercise, and 1, 2, 3, 4, 7, 10, and 14 days postexercise) between control and massage conditions.Setting: University laboratory.Patients or Other Participants: Ten healthy subjects (5 men and 5 women) with no history of upper arm injury and no experience in resistance training.Intervention(s): Subjects performed 10 sets of 6 maximal isokinetic (90°·s⁻¹) eccentric actions of the elbow flexors with each arm on a dynamometer, separated by 2 weeks. One arm received 10 minutes of massage 3 hours after eccentric exercise; the contralateral arm received no treatment.Main Outcome Measure(s): Maximal voluntary isometric and isokinetic elbow flexor strength, range of motion, upper arm circumference, plasma creatine kinase activity, and muscle soreness.Results: Delayed-onset muscle soreness was significantly less for the massage condition for peak soreness in extending the elbow joint and palpating the brachioradialis muscle (P < .05). Soreness while flexing the elbow joint (P = .07) and palpating the brachialis muscle (P = .06) was also less with massage. Massage treatment had significant effects on plasma creatine kinase activity, with a significantly lower peak value at 4 days postexercise (P < .05), and upper arm circumference, with a significantly smaller increase than the control at 3 and 4 days postexercise (P < .05). However, no significant effects of massage on recovery of muscle strength and ROM were evident.Conclusions: Massage was effective in alleviating DOMS by approximately 30% and reducing swelling, but it had no effects on muscle function.     

Distinct immunological signatures discriminate severe COVID-19 from non-SARS-CoV-2-driven critical pneumonia

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Changes in isometric force- and relaxation-time,electromyographic and muscle fibre characteristics of human skeletal muscle during strength training and detraining

HÄKKINEN, K., ALÉN, M. & KOMI, P.V. 1985. Changes in isometric force- and relaxation-time, electromyographic and muscle fibre characteristics of human skeletal muscle during strength training and detraining. Acta Physiol Scand 125, 573–585. Received 26 January 1985, accepted 9 May 1985. ISSN 0001–6772. Department of Biology of Physical Activity and Department of Health Sciences, University of Jyväskylä, Jyväskylä, Finland. Eleven male subjects (20–32 years) accustomed to strength training went through progressive, high-load strength training for 24 weeks with intensities ranging variably between 70 and 120% during each month. This training was also followed by a 12-week detraining period. An increase of 26.8% (P < 0.001) in maximal isometric strength took place during the training. The increase in strength correlated (P < 0.05) with significant (P < 0.05–0.01) increases in the neural activation (IEMG) of the leg extensor muscles during the most intensive training months. During the lower-intensity training, maximum IEMG decreased (P < 0.05). Enlargements of muscle-fibre areas, especially of fast-twitch type (P < 0.001), took place during the first 12 weeks of training. No hypertrophic changes were noted during the latter half of training. After initial improvements (P < 0.05) no changes or even slight worsening were noted in selected force-time parameters during later strength training. During detraining a great (P < 0.01) decrease in maximal strength was correlated (P < 0.05) with the decrease (P < 0.05) in the maximum IEMGs of the leg extensors. This period resulted also in decreases (P < 0.05) of the mean muscle-fibre areas of both fibre types. It was concluded that improvement in strength may be accounted for by neural factors during the course of very intensive strength training. Selective training-induced hypertrophy also contributed to strength development but muscle hypertrophy may have some limitations during long-lasting strength training, especially in highly trained subjects.     

Factors related to postmenopausal muscle performance: a cross-sectional population-based study

The aim of the present study was to investigate cross-sectionally the association of postmenopausal muscle strength with simple performance tests. A random sample of 1,166 naturally postmenopausal women (born 1932–1941) was selected from the Kuopio Osteoporosis Risk Factor and Prevention (OSTPRE) study cohort. Grip and quadriceps strength were measured with strain gauge dynamometers and reported in both absolute values (KPa and kg) and per kilogram of body mass (N cm^–2 kg^–1 and N kg^–1). In addition, two performance tests, ability to stand on one foot and ability to squat down to touch the floor were carried out. A five-category self-assessment of overall health (very good, good, moderate, bad, and very bad) was obtained by postal questionnaire. The women that were able to stand on one foot and able to squat down to touch the floor had greater grip and quadriceps strength than their counterparts (P<0.001 and P<0.03 in ANOVA, respectively). In addition, self-assessed health had a strong positive association with muscle strength in the grip and leg extensor muscles in ANOVA (P<0.001 between very good and moderate or poorer state of health) and regression model (P<0.001). Adjustment for age, duration of menopause, body mass, height, physical activity level, use of HRT, and number of diseases and medications did not change any of the main effects. Also, there were no differences in results between absolute measurement values and values reported per kilogram of body mass. According to the present study, a simple performance test may be useful in the prediction of postmenopausal muscle strength. Furthermore, self-assessed state of health is strongly associated with muscle strength in postmenopausal women.     

Interlimb coupling strength scales with movement amplitude

The relation between movement amplitude and the strength of interlimb interactions was examined by comparing bimanual performance at different amplitude ratios (1:2, 1:1, and 2:1). For conditions with unequal amplitudes, the arm moving at the smaller amplitude was predicted to be more strongly affected by the contralateral arm than vice versa. This prediction was based on neurophysiological considerations and the HKB model of coupled oscillators. Participants performed rhythmic bimanual forearm movements at prescribed amplitude relations. After a brief mechanical perturbation of one arm, the relaxation process back to the initial coordination pattern was examined. This analysis focused on phase adaptations in the unperturbed arm, as these reflect the degree to which the movements of this arm were affected by the coupling influences stemming from the contralateral (perturbed) arm. The thus obtained index of coupling (IC) reflected the relative contribution of the unperturbed arm to the relaxation process. As predicted IC was larger when the perturbed arm moved at a larger amplitude than did the unperturbed arm, indicating that coupling strength scaled with movement amplitude. This result was discussed in relation to previous research regarding sources of asymmetry in coupling strength and the effects of amplitude disparity on interlimb coordination.     

Lymphocyte proliferation in response to acute heavy resistance exercise in women: influence of muscle strength and total work

Little is understood about the immune responses to heavy resistance exercise. The purpose of this investigation was to determine the influence of physical strength and the ability to do more total work on lymphocyte proliferation after an acute bout of heavy resistance exercise. A group of 50 healthy but non-strength trained women were recruited for the study and tested for their one repetition maximum (i.e. 1 RM or maximal mass lifted once). From the normal distribution of strength the top and bottom 8 women [mean age 22.5 (SD 3.1) years] were asked to volunteer to define our two groups (i.e. high strength and low strength). The two groups were significantly different (P<0.05) in 1 RM squat strength [low strength 39.9 (SD 4.6) kg, 0.65 (SD 0.08) kg·kg body mass^–1 and high strength 72.2 (SD 10.7) kg, 1.1 (SD 0.12) kg·kg body mass^–1] but were not significantly different in body mass, age, activity levels, and menstrual status (all in same phase). Each performed a resistance exercise protocol consisting of six sets of 10 RM squats with 2 min rest between the sets. The 10 RM loads and total work were significantly greater in the high strength group than in the low strength group. Blood samples were obtained pre-exercise and immediately post-exercise for test for lactate (significant increase with exercise) and cortisol (no changes) concentrations with no differences noted between groups. Immunological assays on the blood samples determined the incorporation of tritiated thymidine by lymphocytes in responses to concanavalin A (ConA), phytohemagglutinin (PHA), and pokeweed mitogen (PWM). Following the squat exercise, there was a significant decrease in lymphocyte responsiveness to PWM in the high strength but not in the low strength group for both total proliferation and proliferation adjusted per B or T cell. On the other hand, lymphocytes from the low strength group proliferated to a significantly greater extent (adjusted per T cell) in response to ConA and PHA. These data indicate that the heavy resistance exercise protocol reduced the lymphocyte proliferative responses only in the stronger group of subjects. This effect may have been due to the high absolute total work and the greater exercise stress created by the resistance exercise protocol in the high strength group. Therefore, individuals performing at the same relative exercise intensity (i.e. 10 RM) in a resistance exercise protocol may have different immune responses stemming from differences in absolute total work performance. Electronic Publication